Allis, R.G. 1979 Heat flow and temperature investigations in thermal ground. [s.l.]: [s.n.]. Report / Geophysics Division 135 28 p.
Abstract: Detailed temperature surveys of the top 1 m of soil within the Karapiti Thermal Area have been made to test some of the assumptions that have been adopted for estimating the total heat flow from such areas. Results suggest that the existing theory on the transition from conduction to convection requires revision. This transition is now thought to occur when soil temperatures are between 60 deg C and 80 deg C. The revision has little effect on the empirical relationship between heat flow and ground temperature The time of year is found to have a significant effect of the magnitude of the heat flow estimated from aerial infra-red surveys over geothermal areas. The margin of thermal ground is apparently poorly defined by surface temperature, and surveys can only be compared when the surface temperature of non-thermal ground at the time of both surveys is the same